This invention relates to a semiconductor device including a plurality of semiconductor pellets with electrodes to each of which common terminal boards are directly or indirectly connected.
One example of a semiconductor device of this type is shown in FIGS. 1A and 1B. Two transistor pellets 1 are secured through a collector terminal board 2 to an insulating board 31. The emitter electrodes and the base electrodes of the transistor pellets 1 are connected through conductors or lead wires 6 to an emitter terminal board 4 and a base terminal board 5 which are fixedly mounted on the insulation board 31, respectively. The collector terminal board 2, the emitter terminal board 4 and the base terminal board 5 have end portions extending vertically as shown in FIG. 1B, namely, an external lead or extended collector terminal 21, an external lead or extended emitter terminal 41 and a base connecting terminal 51, respectively. An auxiliary emitter terminal 42 and an auxiliary base terminal 52 for base drive are fixedly mounted on an insulating board 32, and are connected through conductors in the form of insulated wires to the emitter terminal board 4 and the base connecting terminal 51, respectively. The insulating boards 31 and 32 are fixedly mounted on a common metal substrate 7. A package 8 (indicated by the chain line) covers the common metal substrate 7. The package 8 is filled with resin to isolate the transistor pellets 1 from the external atmosphere.
The semiconductor device thus constructed suffers from the following two difficulties in a high frequency operation because of an inductance L.sub.s between each transistor pellet 1 and a connecting hole 9 formed in each terminal: One of the difficulties is that an excessively large voltage is applied to the transistor pellet because of a surge voltage V.sub.s =L.sub.x .times.I.sub.c /t.sub.f which is determined from the inductance L.sub.s and the switching time t.sub.f of a transistor pellet 1 (where I.sub.c is the current flowing in the transistor pellet 1). The other is that, when the transistor pellets are used in parallel, the inductance between one of the transistor pellets and the connecting holes 9 is different from that between the other transistor pellet and the connecting holes 9, as a result of which the turn-on of the one transistor is shifted from that of the other, and therefore a large turn-on loss occurs in the high frequency operation.